This invention relates to compositions and interlayers for laminated glazings and more particularly to plasticized polyvinyl butyral resin forming such interlayers.
Polyvinyl butyral (PVB) resin as sheet for use as optically transparent, impact-dissipating interlayer in multilayered laminated safety glazings is well known. Since the glass transition temperature of unplasticized PVB resin is too high for it to be a useful elastomer for impact dissipation in these applications, it is also known to reduce such temperature to a useful range by incorporating a plasticizer in such resin.
In choosing a plasticizer for PVB resin for such applications, it is further known to balance the impact-dissipating and edge stability capabilities of a glazing interlayer by using a mixture where each component of the mixture is better than the other in promoting one of these properties. Representative mixtures and their optimization are disclosed in U.S. Pat. Nos. 4,243,572 and 4,371,586 where aryl adipates in a mixture provide edge stability to the interlayer. Light stability of laminates using plasticized PVB resin, however, is also required for the intended architectural and motor-vehicle window applications involving prolonged exposure to sunlight. Optimizing shock absorbing, edge-delamination-resistant and UV stability properties in an interlayer through choice of an appropriate plasticizer has, to the best of present knowledge, not been accomplished in the prior art.